need help understanding how carb acts and why its starving gas...

[greatestfisherman]

so the time has come for me to get my boat up and running.... took carbs out and cleaned... new plugs etc... test ran the boat and is having trouble with surging and bogging down at WOT... when priming bulb, it runs fine which makes me believe it's and issue with fuel delivery... when boat starts to bog down and as I go to prime the bulb, I can hear the gush of gas dumping into the bowl.... what can cause this issue... stuck needle or stuck float... please explain... im having a brain fart...

ty

 

[dpoff]

Resricted tank vent? Stuck anti-siphon valve that comes off the tank? Just guessing.

 

[Scott Danforth]

In addition to above, could be bad fuel pump diaphragm or flap valves or the inside lining of the hose is deteriorating and adding restriction

 

[greatestfisherman]

def not the vent on the fuel tank... hooked up to a topside tank and no cap and same result...

anti siphon valve does look bad, lots of corrosion on it but appears to be letting gas through fine when I drained the tank prior to the fresh gas that was just got filled...

checked fuel pump and both appears to be in good condition... both diaphragm are not stretch and no holes/leaks... checked the hose lining and no signs of deteriorations...

question: what are the flap valves you are referring to? flap valves in the fuel pump?? pump is only a year old and visually inspecting it, looks good.

could it possibly be a bad prime bulb? when priming it gets hard, to a point where I cant squeeze anymore... however from my understanding the check valves on those should prevent any fuel to flow back into the tank... in my case, after a few minutes its back to soft which I want to say its an air leak or bad bulb or is this normal? the way I have the bulb installed is before the separator and not before the engine like supposed to... was like this when I bought the boat a year ago.

 

[211libwtfo]

Anti siphon valve $5 part

 

[greatestfisherman]

update: going to redo the fuel line and test out the bulb again... im at work right now and just trying to get all info I can together before working on boat... going to redo and get the bulb installed 3 ft from motor like suppose to between the motor and separator.... going to replace fuel pump too and check the siphon valve to make sure its not restricting... ill keep you guys posted....

 

[greatestfisherman]

so after doing the above, bulb and gas is no longer an issue... stays firm throughout the boating session without having to prime... stupid me when in the water, took the cowl off to fine tune the idle, I accidently disconnected one of the coil from the spark plug... after boating around 5 mins or so and noticing a loss of power, decided to head back onto the ramp.... took cowl off again and finally noticed the disconnected coil...

question: do I need to worry about anything? I assume that with no spark, the cyclinder was being flooded with gas and oil... what should I do before starting up next time?

ty

 

[greatestfisherman]

anyone with any suggestions?

 

[Newbie@boats]

Turn the key and run it.

 

[greatestfisherman]

from one problem to another... now that everything prior is resolved, I now have other problems... when running at high speeds some times the boat seems to be running not on all cyclinder... for ex. when going WOT, only able to reach 40000 rpm instead of 50000+... when this happens I flip the choke and the boat kicks and picks up almost instantly giving me a whiplash and it would run 50000+ rpm... this will happen a couple times a day (12hr fishing day)... also now my boat is idling like crap... not that its choking or coughing etc.. as if its running low on gas after idling for a few minutes... I can assure you guys that the carb is clean as I have taken it apart 3 times to clean it prior... not sure where to start looking at this point... anyone with any suggestions?

thanks again.

 

[99yam40]

your post points at carbs need another cleaning, does not take much trash to mess things up

need to find out where that trash is coming from.

and none of these motors should be hitting 40k or 50K RPM

 

[greatestfisherman]

what in the world 40k lol... I meant 4k and 5k... anyways, damn the carbs again... this is driving me nuts... I will take it apart again and clean it... thanks for all your help...

 

[greatestfisherman]

so im in the transition of reassembling one of the carbs but noticed before undoing the big brass screw that covers the air mixture screw is was not screwed all the way in... am I suppose to screw it all the way down until its tight or leave a pocket between the air screw and jets ports...???

 

[greatestfisherman]

never mind figured it out... it should be tighten down... ty and mostly thanks to yam...

 

[ClassicAQ]

Those brass screws, along with all other screws on the carbs, have a specific torque spec. Look at your service manual under specifications chapter. I believe the torq is 5 or 6 lbs. You're not dropping a cylinder if the engine responds as you supply a rich mix (choke). You've got a fuel system issue, not compression issue.

If you're pulling carbs and cleaning yourself, pull every jet out and clean. Make sure you can see through each jet before installing. Once you re-install carbs, you then need to time and sync the carbs. If you're not sure how, consult your service manual. If the engine is idling rough then you need to adjust the idle mix screw of each barrel of each carb. I didn't see you list the year/model of your engine so I have no idea what you spec mix screw setting should be.